Cytoarchitectural Analysis of Epithelial Sheets Formed in Vitro by Hepatic Tumor Cells Possessing Defined Intermediate-sized Filament Cytoskeletal Abnormalities

Established 72/22 rat hepatic tumor cells, which bear well-characterized cytoplasmic abnormalities of intermediate filament (IF) network organization, form monolayer "sheets" of tightly juxtaposed epithelial cells at high culture population densities. The distribution of desmosomal complexes and their affiliated tonofilaments, as well as the regulation of cytokeratin/vimentin IF and actin microfilament contents were assessed during construction of this in vitro "epithelium." 72/22 cells formed desmosomal junctions throughout the length of the cellular perimeter. Compared with low population density cultures, fully confluent sheets of 72/22 cells exhibited a down-regulated cytoskeletal actin content and increased level of cytokeratin synthesis. Despite gross IF cytoarchitectural abnormalities, 72/22 cells normally modulated the content of specific structural elements within both the IF and microfilament networks in response to increasing cell-cell contact. Furthermore, these data support the concept that neither the structural integrity nor the topographic distribution of the desmosome array are dependent on tonofilament anchorage or IF scaffold organization.